Pressure sensitive record materials



Patented Apr. 10, 1951 1 PRES-SURE SENSITIVE si com) MATERIALS 1 Barrett K; Green and- Robert Ws-San'dberg; Day ton, ohio assignors to The N ationaleflashzrRegs .ister.-Company, Dayton, Ohio, atonpOrationeof sMaryland No Drawing. ApplicationJill'y 13, 1948, Serial N0. 38,547

. 28 Claims. :1

This invention relates a to pressure-sensitive recordmaterial, and more particularly. pertains to such material having minute particles of. two kinds of substances-which are color reactiveon contact, .one: of the substances being in :liquid form and the other being in solid form, the particles of the two substances bein'grarranged. in proximity in profuse numbers but insulated from contact by material. rupturablewhen pressure is applied, which. pressure acts to bring the two kinds of substances together .at thepoints of rupture'to produce-ya distinctively colored localized mark.

The record material of this inventionalthough adapted for response to. stylus .pressures, is particularly adapted for response to .pressures. applied; in; impact gprinting operations such as. by the-striking: or: pressing .of type thereagainst and in .that respect isanimprovementover the. record material of .Barretti- K. Green's copending. application. Serial No. 784,938,..filed November 8, 1947, for Pressure Sensitive Record Material; now Eatent No. 2,505 ,470.

The record; material disclosed therein required thei'bringing together, by pressure, of two :kinds of; solid: particles. embedded 'in a rupturable, solid jnsulatingfilm. .Thelow. mobility f.iS1l0h1SO1ld particles, rendered that. record material .more sensitive. topressures caused :by drawing a stylus thereover than tdpressuresderivedfrom the impact of type. .This novel. record..material also is an, improvement over .that :record:,material disclosed. in United .States .zLettersv Patent. No. 2,299,693, patented on October 20, 1942, on the application; of Barrett K. .Green. That patent discloses.pressureesensitiverecordmaterial, especially adapted for impact Work, such material in- .cluding a rupturable insulating medium in which are interspersed. liquid droplets of two kinds which reacton contact to form color. Theliquid droplets 'includedsolid color-.-forming materials dissolved in an ionizing medium, glycerine, which reacted toproduce color on contact by interchange of ions. Any liquid ionizing medium available foruse in-such asystem is hygroscopic making the. record material unduly sensitive to moisture.

The present invention provides a record material ..with exceptional: response to impact ,pressures and one having remarkable-stability as no ionizing liquid is required. The, liquid used to dissolve the active color ingredient in the liquid reactant substance .is a non-ionizing inert oily type of material which is. non-hygroscopic and is used solely to dissolve the. active ingredient and to obtain. easier. release and greater mobility of thedroplets when-the supporting film is ruptured.

Because of the. mobility of the released liquid droplets. at: points. ofrupture of the insulating medium,- the .newv record material. is: highly. sensifiveiibcjth .to'. drawing; and tolimpact :pressures yet :it -isresistant to destructive influences-. em countered rinsordinaryr.enriroment andv normal handlingioperations; fill-111s .thenew reoordmaterial-combines thexbe'st .characteristicsofiknown pressure responsive *record materials by providing. a novel .liquid solidz. reactant; structure. The principalzobj ect otxthefinvention to; provide.arpressureesensitiverecordsmaterial: on which anmark of. distinctive color. may bejproduced-rby the mere...applicationcof.localized: pressures; said material 2 including ecoloreform-ingu substances-,r 'of two kinds, one beings-solid and the .othembeing liquid, the. two; substancesi normally v:beingzfhjeld insulated; fromsreaction contact by..-,a;rupturah1e insulating;medium-,untilemarking;pressures. rupturetheuinsulating.mediumzatupoints:of pressure .to bring about local contact of .they twosubstances :to producmna mark.

' Another objectgofathe invention ,isto ..prov.ide .a record 'materiaLi-n-WhiCh one :of zthecolor reactantssubstanees is dissolved. in.:.anon-ionizing..oily=..liquid which may be dispersedgasrdroplets 'inzarrupturable solidinsulatingfilmso (as :to'; be: readily available and mobile locally to make contact with the other solid.reactant.-ma-

:detail in the ,xfollowingz.zspecification. Theyzin- .vention; is L clearlyzcdefined Hand pointed out-12in ithe -zappended';claims.

;.In';.the; preferred :iorm .zofz'this' vinventiom the iliquid droplets; of cooler-.1 reactant are .adispersed ;in-sasfilm-formingzsubstancex which is..::applie.deas

2a coating itoz-zazpaper vsweb and .rdried :.:thereon leaving the liquid droplets entrapped therein. zThezsolid-zcolorireactant particles; acting .a's-adsorbentsaarelikewise-dispersedriir azfi-lm-forming .:substance.-.whi'ch is applied as asecond-ovenlying coating; Both.5films arerupturableg'to --force;2the reactant substancesitogether.

Of the reactant materials employedmthel liquid droplets; contain ran .organiclsubstancexwhich is an :electr-on .adonorraromatic :rcompound shaving a :double :..bond;.-syst.emwhichwis :convertedyto 5a more highly polarized iconiu ateddormuupon taking vpart .intan electron donorg-acceptorazadsorptionIchemicalreaction, giving it a distinctive color, and the solid particles are of an inorganic substance which is an acid relative to the organic substance so as to be an electron acceptor when in adsorption contact therewith. The solid material is in fine particle form in order to furnish a large reactant surface per unit area of the record material, which enhances the depth of color produced in the record material.

The film-forming substances are derived from hydrophilic colloid materials that form pressurerupturable films.

Although in the preferred form of the invention a single kind of solid reactant particle substance is used, such as =Attapulgus clay, or attapulgite, it is within thescope of the invention tomixtwo 'or more kinds of solid reactants together, such as magnesium trisilicate and attapulgite, or to mix attapulgite with sodium aluminum silicate zeolites, which together act as adsorbents upon which color reactant adsorbates dissolved in the liquid droplets may be adsorbed.

Likewise the adsorbate substance may include one or more kinds of reactant such as crystal violet lactone, which is 3,3 bis(p-dimethylaminophenyl) -6-dimethylaminophthalide, and tetrachloro malachie green lactone mixed together and dissolved in the oily liquid.

The web used as a support may be paper or other material suitable as a. record base. For instance, either cardboard, glass, metal or wood maybe used if desired. The total thickness of the pressure-sensitive film need be no greater than from .001 to .002 of an inch so it may be supported on very thin paper stock. By placing a number of such'thin-coated paper sheets in superimposed-relation in a typewriter a number ofprinted copies of typewritten material may be made without the use of a typewriter ink ribbon or carbon manifold paper as is now the 'common practice. I 1

As it-is difficult, if not impossible, to show the exact structure ofthis coating by use of a drawin 'none accompanies this specification.

In the followin e amples, there will be described'embodiments of this invention by which the objects of the invention have been successfully attained. Y r l r Example 1.The following embodiment of this invention constitutes the best mode of applying the principles thereof as contemplated up to the present time and may be considered the preferred embodiment.- It. comprisesa base web of paper, or thelike, on one surface of which two coatings are applied, the first or undercoating being an insulatingfilm in which are entrapped a profuse number of liquid droplets in :which acolor reactant substance is dissolved.

These droplets are, on the average, of the order of from 1 to 5 microns in diameter and are spaced apart'ion the average, a distance of the order of micron. The preferred thickness of this first =coating, when dry, is of the order of .001 of an inch. V r

The first coating is made by dissolving one part by weight of animal gelatin, having an isoelectric point of pH Band a jelly strength of '275 grams as measured by the-Bloom gelometer,

in chlorinated diphenyl.

This solution-of crystal violet lactone, which is 3,3 bis(p -"dimethylaniinophenyl, 6 dimethylamino phthalide, in chlorinated diphenyl is made by dissolving three parts by weight of the crystal violet lactone in ninety-seven parts by weight of chlorinated diphenyl which has a chlorine content averagin 48 per cent by weight. This chlorinated diphenyl solution is heated to the temperature of the gelatin solution before it is added thereto and emulsified.

The emulsion is applied while still hot, or if allowed to cool after reheating to F. and is dried either under normal atmospheric conditions or by artificial means such as a hot air blast or on a heated drying drum such as is commonly used in paper coating machines. It is considered that drying under normal atmospheric environment gives a somewhat :better Water resistance to the dried film or coating in which the chlorinated diphenyl solution droplets are entrapped.

The dried undercoatingis next treated to drive the droplets out of the top surface layer and into the interior of the film so as, in effect, to form an impermeable surface skin thereon. This is ac complished by wetting the surface with water at room temperature, that is from 7080 Fahrenheit, which water has had added thereto 1 per cent by weight of formaldehyde and 0.1 per cent by Weight of a wetting agent such as dioctyl ester of sodium sulfosuccinate. The wetting should be allowed to persist for several minutes and thereafter the film is dried in a low humidity atmosphere. The surface wetting may be accomplished byfioating the coated paper on the water, coated face down, or by carrying it on a partially submerged drum with the coated surface facing outwardly. The formaldehyde may be omitted, if desired' Y w The second, or overcoating, th'e'n'is applied to the dried undercoating. In making the second coating 20 per cent, Icy-weight, of paper coating starch in water is cooked at 200 Fahrenheit for 15 minutes and cooled to room temperature. Separately, 1 part by Weight of attapulgite is dis persed in three parts by weight of water by use of a ball mill or equivalent. 'Four parts, by weight, of the attapulgite dispersion mixed with one part, by weight, of the starch solution. The resultant mixture is applied, at room temperature, as an overcoating to the prepared paper having the gelatin coating dried thereon. This starch-clay overcoating is applied in any convenient manner, as by a paper coating machine. This overcoating when dry should have a thickness of the order of .0005 of an inch.

The thickness of the undercoating and the overcoating may be varied somewhat without interfering gre'atly'with the sensitivity of the material, such variationrange being of the order of 25 per cent in either direction.

This record material when finished has a substantially white appearance and produces a dark blue mark which sharpl defines the area of pressure or impact. 1

The impact of a markinginstrument on the surface of this record material locally releases the oily droplets from the gelatin film and forces them into contact with the overlying attapulgite particles. The needle-like crystal aggregate structure of attapulgite prevents any substantial masking of it by the starch binder, thus leaving the attapulgite available to adsorb the color reactant crystal violet-lactone from the released oil. Therefore, in this coating system the attapul'gite solid particles are held in a non-masking or noninsulating binder whereas the oil-carried other 7 reactant is protected as entr'apped 'driopletsin thegelatin insulating v The "compound crysta'lviolet-lactohe has th structure a)2 and the process of rnakingritv is described in. United States Letters P'a'tentNoL 2,417,897, is sued March 25, 1947, on theapplicationfof lClyde S. Adams, filed June 16, 1945, although the com pound is incorrectly, namedlin said patent as 3,3 bis(4-dimethylaminophenyl) -6-dimethyla= ingpla'ce of the crystal yiolet'lactone-of Example, land, in the same, amount.' Thisvgives a substantially' white record material producing a green mark when the pressure isapplied. This green color is not as intense as the blue given by crystal violet lactone.

Example 3.-Another embodiment of the invention is the use of tetrachloro malachite green lactone, that is to say 3,3 bis(p-dimethylaminophenyl) 4,5,6)? tetrachloro phthalide, having the structure in place of the crystal violet lactone of Example 1 and in the same amount. This gives a substantiall white record'material producing a green mark when pressure is applied.

Emample 4.-Another embodiment of the invention is the use of 3,3 bis(p-diethylaminophenyl) fi-dimethylamino phthalide, having the structure aims-sam in place of the crystal violet llactone of Example v2 1 andin the same amount." This gives ,a substantially white record material producing .aublue. markwhen pressure is applied.

Example 5.-Another embodiment of the invention is the use of 2,4 bisEp-(p-dimethylaimihophenylazo) anilinol-6-hydroxy sym. triazine, having the structure N H H0 o n QN ;N--N omn in place of the crystal violet lactone of Example I 1 but using only one-sixth as much by weight. The normal color of this record material is dark yellow and upon pressure being applied it turns to a bluish gray.

In Examples 1 to linclusive the attapulgite can be replaced with a synthetic zeolite material of the sodium aluminum silicate type preferably" having a maximum particle size of "10"microns V and used in essentially the same amount by, weight as specified in Example 1 'forthe attapulgite. For use with'the zeolitetype of ad-- sorbent, gelatin, methyl cellulose, polyvinyl al cohol; and casein'may besubstituted for the starch of Example 1 as a binder.

In Examples 1 to 5inclusive, whether attapulgite or the sodiumhe'olite is "u's'ed,there may be substituted for the starcha mixture of starch, casein, and a synthetic latex'made'of butadienestyrene oopolymer material. Insuc'h'a' binder when dried with the attapulgite or zeolite 'mate-' rial therein, the amount of starch should be 7 per cent, the amount of casein should be 1 per cent, and the amount of latex should be 7 per cent all by weight with respect to the weight of theattapulgite or zeolite material; In making such'a binder a starch solution ismade as described in Example 1 and allowed to cool. Next. one part of casein is dispersed in"'two 'parts"of" cold'i'water, by Weight, and allowed to swell for" one-half hour, after which sevenmore parts of cold water-and /10 of'a part 'ofammonium hy droxide of 25 Beaum are added; This casein dispersion is heated on a water bath of Fahrenheit for 15 minutes and then allowed to" cool. The latex used contains 45 per cent of solids in water. The attapulgite or zeolite material to be used is dispersed in water as set out in Example 1 except the water contains'0.2%" of sodium py rophosphate. To 10 parts by weight of the dispersed adsorbent, eliminating the'weight of the water, is added 3.5 parts by weight of the starch solution, 1.6 parts by'weight of the latex, and 1 part by weight of the casein solution. This binder material is characterized by greater adhesion'to. the adjacent coatingandby excellent properties as far as the access of'theadsorbent material to the action of the liquid color reactant droplets is concerned.

In Examples 1 to 5 the attapulgite may be replaced with an equivalent amount of halloysite, and in Examples 1 to 4 the attapulgite may be replaced by an equivalent amount of magnesium trisilicate. Mixtures of the adsorbents will do as well as the individual adsorbents.

With respect to the zeolite material the sodium of the specified sodium aluminum silicate may be replaced with other cations such as nickel, copper, iron, zinc, mercury, barium, lead, cadmium and potassium to give zeolites with equivalent or better color reactant qualities.

The exchangeable calcium cations on natural attapulgite may be replaced by other cations to give workable adsorbents in the same way as noted for the zeolites. In addition hydrogen may be substituted for the calcium exchange cations of attapulgite.

The adsorbent material should be accessible to the liquid droplets containing the color reactant material to be adsorbed thereon and the action of the coating binder tends to mask the exterior surface available on such adsorbent particles. The needle-like aggregates of attapulgite and the porous structure of zeolites, contain interiorly active surfaces, not masked by the binder, which are left available for adsorbing the color reactant in the liquid droplets and, hence, these types of adsorbents are particularly suited for the novel structure which is the subject of this invention. Halloysite and magnesium trisilicate seem to be of such structure as has available interior adsorbent surfaces and therefore are given as substitute materials to act as the adsorbent material of the system.

The methods and process of making the pressure-sensitive record material as disclosed herein are disclosed and claimed in the copending application of Barrett K. Green and Robert W. Sandberg, Serial No. 38,548, filed July 13, 1948.

It is understood that the pressure-sensitive record material described herein is susceptible of considerable variations without departing from the spirit of the invention.

What is claimed is:

1. Pressure-sensitive record material including the combination in a coating on a base web of color-forming substances of two kinds, one kind being solid and the other kind being liquid, said liquid kind being held insulated from contact with the solid kind by being profusely dispersed in minute droplets in a solid rupturable film on the exterior of which is deposited a film bearing particles of the solid kind, the application of localized pressure to the record material rupturing the film at points of application and there bringing the color-forming substances together, whereby a distinctively colored mark is produced by mere application of localized pressure, the liquid substance including an electron donor aromatic organic compound having a double bond system which is convertible to a more highly polarized conjugated form upon taking part in an electron donor-acceptor adsorption chemical reaction, giving it a distinctive color, and the .solid substance being an inorganic material in fine particle form providing a large adsorbent surface area and said inorganic material being an acid relative to the organic compound and acting as an adsorbent therefor so as to be an electron acceptor when the organic compound is in adsorption contact therewith.

2. oflherecord material of claim 1 in which the liquid color-forming substance includes as the active ingredient 3,3 bis(p-dimethylaminophenyl) -6-dimethylamino phthalide having the structure 3. The record material of claim 2 in which the solid color-forming substance is attapulgite.

4. The record material of claim 1 in which the solid color-forming substance is attapulgite.

5. The record material of claim 1 in which the liquid color-forming substance is dispersed as droplets in a gelatin film.

6. The record material of claim 1 in which the liquid color-forming substance is dispersed in minute droplet form in a gelatin film supported by a base web, and in which the solid color-forming substance is dispersed in fine particle form in a binding coating applied over the gelatin film.

7. The record material of claim 1 in which the liquid color-forming substance includes as the active ingredient 3,3 bis(p-dimethylaminophenyl) phthalide having the structure (0 mm Unmet, C

8. The record material of claim 1 in which the liquid color-forming substance includes as the active ingredient 3,3 bis(p-dimethylaminophenyl) 4,5,6,7 tetrachloro phthalide having the structure 9. The record material of claim 1 in which the liquid color-forming substance includes as the active ingredient 3,3 bis(p-diethylam inophenyl) G-dimethylamino phthalide having the structure (01mm: Omani), C

. 10. The record material of claim 1 in which the liquid color-forming substance contains as the eactive ,ingredient2,4 :bis [p- (p-dimethylarninoazo) :anilinol-G hydroxy sym. .triazine, having the structure 11. The recordmaterial of claim 1 in which the liquid color-forming substance includes an oily,

non-evaporating solvent for asolid color-forming reactant carried therein in solution.

12. The record material oi claim 11 in which the liquid color-forming solution is dispersed in gminute droplets in a thin rupturable gelatin film coated on a supporting'web.

13..The record material of claim 12 in-which the solid color-forming substance is carried dispersed in a binder film coated on top of the gelatin film.

ing the combination of a supporting web; a continuous rupturable solid insulating film applied thereto said film containing dispersed therethrough a profusion of minute liquid color-forming inclusions; and a coating on the outer surface of the insulating film, said coating containing a profuse number of solid color-forming particles which, when brought into contact with the liquid inclusions by application of localized pressure to the record material which ruptures the insulating film and coating, react with said liquid inclusions to form a distinctively colored mark at said points of localized pressure, the liquid inclusions include an electron donor aromatic organic compound having a double bond system which is convertible to a more highly polarized conjugated form upon taking part in an electron donor-acceptor adsorption chemical reaction, giving it a distinctive color, the solid particles being an inorganic substance of such fineness as to provide a large adsorbent surface area, said inorganic substance being an acid relative to the organic compound so as to be an electron acceptor when in adsorption contact with said organic compound, and the film being derived from a hydrophilic colloid material.

15. The record material of claim 14 in which the liquid color-forming substance includes as the active ingredient 3,3 bis(p-dimethylaminophenyD-G-dimethylamino phthalide, having the structure w ah 14. Pressure-sensitive record material includ i9 9. The recordmaterial of claim 14 in which the liquid color-forming substance is dispersed in minute droplet form in a gelatin film supported .by a base web, and in which the solid color-forming substance is dispersed :in fine particle form in a binding coating applied over the gelatin, film.

20. The record material of claim 14 in which the liquid color -forming substance includes as the active ingredient 3,3. bis (pwdimethylaminophenyl) phthalide havingthe structure 21. The record material of claim 14 in. which the liquid color-forming substance includes as the active ingredient. 3,3 bis(p-dimethylaminophenyl) 4,5,6}? tetrachloro phthalide having the structure 22. The record material of claim 14 in which the liquid color-forming substance includes as the active ingredient 3,3 bis(p-diethylaminophenyl) -6-dimethylamino phthalide having the structure (OzHs) 2N- N (Cz s)2 24. The record material of claim 14 in which the liquid color-forming substance includes an oily, non-evaporating solvent for a solid colorforming reactant carried therein in solution.

25. The record material of claim 14 in which the supporting Web is paper.

26. A pressure-sensitive record material including the combination of a web of paper; a ruptur- 1 I able thin solid film coated on one side of the paper to which it is adherent, said film havin dispersed internally thereof a profusion of minute discrete liquid inclusions of a material which produces a color when in contact with a certain class of color-forming solid substances; and a rupturable coating on said film containing a profuse number of minute solid particles of one or more of the class of said color-forming substances embedded therein, localized pressure on said record material rupturing the film and coating to brin together locally at the pressure points the solid particles and liquid inclusions to form a distinctively colored mark, the liquid inclusions including an electron donor aromatic organic compound having a double bond system which is convertible to a more highly polarized conjugated form upon taking part in an electron acceptor-donor solid surface chemical reaction, giving it a distinctive color, the solid particles being fine to provide a large adsorbent surface area, said solid particles being an acid relative to the organic compound so as to be an electron acceptor when the organic compound is in adsorption contact with it, and the film being derived from a hydrophilic colloid material.

2'7. The structure of claim 1 wherein the liquid 12 inclusions contain more than one kind of color reactant.

28. The structure of claim 2'7 in which one of the color reactants in the liquid inclusions is 3,3 bis(p-dimethylaminophenyl) -6-dimethylamino phthalide and another color reactant in the same inclusions is 3,3 bis(p-dimethylaminophenyl) 4,5,6,7, tetrachloro phthalide.

BARRETT K. GREEN. ROBERT W. SANDBERG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,781,902 Gill Nov. 18, 1930 2,168,098 Groak Aug. 11, 1939 2,299,693 Green Oct. 20, 1942 2,299,694 Green Oct. 20, 1942 2,374,862 Green May 1, 1945 OTHER REFERENCES Hauser et al.: Color Reaction between Clays and Amines, July 1940, pp. 1811l4. 

1. PRESSURE-SENSITIVE RECORD MATERIAL INCLUDING THE COMBINATION IN A COATING ON A BASE WEB OF COLOR-FORMING SUBSTANCES OF TWO KINDS, ONE KIND BEING SOLID AND THE OTHER KIND BEING LIQUID, SAID LIQUID KIND BEING HELD INSULATED FROM CONTACT WITH THE SOLID KIND BY BEING PROFUSELY DISPERSED IN MINUTE DROPLETS IN A SOLID RUPTURABLE FILM ON THE EXTERIOR OF WHICH IS DEPOSITED A FILM BEARING PARTICLES OF THE SOLID KIND, THE APPLICATION OF LOCALIZED PRESSURE TO THE RECORD MATERIAL RUPTURING THE FILM AT POINTS OF APPLICATION AND THERE BRINGING THE COLOR-FORMING SUBSTANCES TOGETHER, WHEREBY A DISTINCTIVELY COLORED MARK IS PRODUCED BY MERE APPLICATION OF LOCALIZED PRESSURE, THE LIQUID SUBSTANCE INCLUDING AN ELECTRON DONOR AROMATIC ORGANIC COMPOUND HAVING A DOUBLE BOND SYSTEM WHICH IS CONVERTIBLE TO A MORE HIGHLY POLARIZED CONJUGATED FORM UPON TAKING PART IN AN ELECTRON DONOR-ACCEPTOR ADSORPTION CHEMICAL REACTION, GIVING IT A DISTINCTIVE COLOR, AND THE SOLID SUBSTANCE BEING AN INORGANIC MATERIAL IN FINE PARTICLE FORM PROVIDING A LARGE ADSORBENT SURFACE AREA AND SAID INORGANIC MATERIAL BEING AN ACID RELATIVE TO THE ORGANIC COMPOUND AND ACTING AS AN ADSORBENT THEREFOR SO AS TO BE AN ELECTRON ACCEPTOR WHEN THE ORGANIC COMPOUND IS IN ADSORPTION CONTACT THEREWITH. 